Ruud U96VA0702317MSA Error Code 55: High Pressure Switch Closed, Inducer Off
What Does Code 55 Mean?
Code 55 on the Ruud U96VA0702317MSA means the high-pressure switch is closed while the inducer is not running. Before each heat cycle the Integrated Furnace Control verifies this switch is open; finding it already closed fails that safety test, because the switch should only close once the inducer establishes draft.
This is a critical fault and no gas heat is allowed, though cooling and fan can run. It is the high-pressure equivalent of code 44 on the low-pressure switch — both describe a pressure switch closed when it should be open — and the counterpart to code 57, where the high-pressure switch fails to close while the inducer runs at high speed.
The most common cause is a faulty switch stuck closed or one deliberately bypassed in the field, which is a dangerous and potentially illegal modification. Abnormally high negative vent pressure can also close it. Inspecting, replacing, or un-bypassing a pressure switch is technician work.
What You'll Notice
- The furnace will not start heating and shows code 55 during the pre-start check
- The fault appears before the inducer runs
- Cooling and fan may still operate
- The code returns on each heat call until the switch or its cause is fixed
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Pressure switch stuck closed or bypassed | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician checks whether the high-pressure switch is stuck closed or has been physically bypassed, and inspects the switch, wiring, and hoses. They also verify the venting and terminations meet the installation instructions.
If a bypass is present, they remove it and correct the reason it was added — for example venting that exceeds the maximum length — rather than simply restoring the switch.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace shows code 55 and will not begin heating
- You suspect the high-pressure switch has been jumpered or bypassed
- The fault recurs on every heat call after resets
Frequently Asked Questions
What is the difference between code 55 and code 44?
They describe the same problem on different switches — a pressure switch closed while the inducer is off — with 55 for the high-pressure switch and 44 for the low-pressure switch.
Can abnormal vent pressure cause code 55 without a bad switch?
Yes, unusually high negative pressure in the vent can close the switch with the inducer off, though a stuck or bypassed switch is the more common cause, so a technician should confirm which it is.
✓ Verified against manufacturer service manual — March 2026